Head to your device's Settings, then tap General.

Tap iPhone Storage.

Select Moody Radio from the list of apps.

Tap on "Offload the app" option and confirm. This will delete the app but its documents data will still be there.

Then tap Delete App and confirm. This action will delete any leftover documents and data.

Once the app is deleted, press and hold the Side/Top button and either volume button until the power off slider appears.

Drag the slider to turn shut down your device completely.

After your shuts down, wait a couple of minutes.

Press and hold the Top (or Side) button again until the screen turns on.

Switch your device back on and install Moody Radio from the App Store.